Chapter: Fiber optics and Laser instruments : Optical Fiber and Their Properties
PIN Diode Photo detectors: Principle, Construction, Working
Photo detectors
PIN Diode
Principle:
This is a
device used to convert the light energy into electrical energy.
Under the
reverse bias condition, if the light ray is incident over the intrinsic region,
then it will produce the electron hole pair.
The
accelerated electron-hole pair charges carrier produce the photo-current.
Construction:
It consists of three layerssuch as p, n and
intrinsic region with proper biasing.
The P and
N region are heavily doped.
The
intrinsic layer is slightly larger than both the p-type and n-type for receive
the light photons.
Working:
The PIN
diode is heavily reverse biased.
When a
photon of higher energy is incident over the larger width intrinsic
semiconductor layer, then the electron hole pairs are created.
The
mobile charges are accelerated by the applied voltage, which gives rise to
photo current in the external circuit.
It is a
linear device because the photo-current is directly proportional to the
incident optical power on the PIN photo-diode.
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